Chapter 25. Nucleotide Biosynthesis Flashcards
the enzyme that catalyzes the reduction of all four ribonucleotides to deoxyribonucleotides.
Ribonucleotide reductase
a protein domain that surrounds ATP and orients it for nucleophilic attack at the gamma phosphate. Enzymes with these domains catalyze the formation of carbon-nitrogen bounds through acyl phosphate intermediates.
ATP-grasp fold
A nitrogenous base that is a six-membered heterocyclic ring containing two nitrogen atoms and four carbon atoms; the pyrimidine derivatives cytosine, uracil, and thymine are found in nucleotides and nucleic acids.
Pyrimidine nucleotide
Birth defects, which can result from insufficient folic acid in the mother's diet, characterized by the incomplete or incorrect formation of the neural tube early in development.
Neural-tube defect
the enzyme that catalyzes the committed step in purine synthesis, which is the displacement of pyrophosphate in 5-phosphoribosyl-1-pyrophosphate by ammonia of yield 5-phosphoribosyl-1-amine with the amine in the beta-configuration.
Glutamate phosphoribosyl aminotransferase
a nucleotide precursor to uridylate and cytidylate formed by the reaction of orotate with 5-phosphoribosyl-1-pyrophosphate (PRPP).
Orotidylate
An immunological disorder, caused by a deficiency of adenosine deaminase, characterized by severe recurring infections, often leading to death at an early age.
Severe combined immunodeficiency (SCID)
in general, a pathway that synthesizes the final product from preformed components; nucleotides can be synthesized in a salvage pathway by attaching purine bases to PRPP.
Salvage pathway
A syndrome, associated with a lack of the purine salvage pathway enzyme hypoxanthine-guanine phosphoribosyl transferase, that is characterized by compulsive self-destructive behavior, mental deficiency, spasticity and aggressiveness toward others.
Lesch-Nyhan syndrome
An activated form of ribose that accepts bases in nucleotide synthesis.
5-phosphoribosyl-1-pyrophosphate (PRPP)
A nitrogenous base that includes a pyrimidine ring fused with a five-membered imidazole ring; the purine derivatives adenine and guanine are found in nucleotides and nucleic acids.
Purine nucleotide
the enzyme that catalyzes the regeneration of tetrahydrofolate from dihydrofolate formed in the synthesis of thymidylate.
Dihydrofolate reductase
A disease characterized by inflammation of the joints and kidneys due to the precipitation of abnormally high levels of sodium urate, a breakdown product of purines.
Gout
The enzyme that catalyzes the synthesis of carbamoyl phosphate from bicarbonate and ammonia, the first step in de novo pyrimidine biosynthesis
carbamoyl phosphate II (CPS II)
One of a class of birth defects characterized by the incomplete or incorrect formation of the neural tube early in development.
spina bifida
